1. Field of the Invention
The present invention generally relates to a position signal processing apparatus, and more particularly to a motor position signal processing apparatus.
2. Description of Prior Art
Servomechanism system refers to a system for controlling the position, speed or acceleration of a mechanical system by a close loop control method. In general, a servo system usually has several main parts including a plant, an actuator, and a controller, and the plant is a controlled object such as a mechanical arm or a mechanical working platform. The main function of the actuator is to supply power to the plant by pneumatic, hydraulic, or electric driving method. If the hydraulic method is adopted, the actuator is generally called a hydraulic servo system. At present, a vast majority of servo systems adopt the electric driving method, and the actuator includes a motor and a power amplifier, and a special design applied to a motor of the servo system is called a servo motor, which usually includes a position feedback device such as an optical encoder or a resolver. The servo motors mainly used in the industry include DC servo motors, permanent magnet AC servo motors and induction AC servo motors, and the permanent magnet servo motors are used most extensively. The function of the controller is to provide a close circuit control such as a torque control, a speed control and a position control for the whole servo system. In general, the present industrial servo drives usually include a controller and a power amplifier.
The aforementioned servo motors usually include a position feedback device for providing three types of signals through an optical encoder, and the three types of signals are: (1) Incremental signals A, B provided for obtaining the information of the moving speed of a controlled object; (2) Signals U, V, W using a combination of logical states of the signals U, V, W to represent absolute position information of an actual mechanical position of a controlled object; (3) Signal Z (Index Pulse) being a reset correction signal that provides constant mechanical position information. For the types of signals, these three signals are generally line drivers, wherein the signals U, V, W only provide the information of a start position of a signal processor (DSP or MCU) when the controlled object is started. After the optical encoder operates with the controlled object, the signal processor (DSP or MCU) primarily processes the incremental signals A, B and the signal Z (Index Pulse). Therefore, the signal processor (DSP or MCU) requires at least six pins for the interface to receive signals of the optical encoder, and such arrangement occupies a large portion of the I/O performance of the processor. Further, the power supply of the optical encoder is generally separated from the signal processor (DSP or MCU), and thus an additional separator is required, and the external circuit requires six sets of circuits for processing the signals of the optical encoder. As a result, the level of complexity of the circuits, the size of the circuit board, and the cost are increased significantly.